It is desirable in a burner to have as high an efficiency as possible since, traditionally, burner efficiency is relatively low. In burners such as the burner shown U.S. Pat. No. Re. No. 28,679, naming the same inventor, a horizontally positioned grid burner is utilised. The use of such a burner in certain applications has an efficiency that is relatively low. Further, such a burner configuration is inoperable for practical purposes where a horizontal rather than a vertical configuration for the heat exchanger is required.
Yet another disadvantage with existing burner assemblies is that unnecessary electrical power can be consumed in ignition. Ignition utilises electrical discharge from the battery or batteries connected to the ignition electrode and the discharge occurs until the temperature for self sustained combustion is reached. In previous heaters, ignition was independent of the temperature of the burner and operated for a predetermined time period. Since the temperature for self sustained combustion may be reached much more quickly when the burner is warm, the additional time for electrode operation was frequently unnecessary and the electrical current expended from the battery is wasted. A further problem with the aforementioned timed electrode discharge is that the burner can become dangerously hot.
Yet a further disadvantage of previous burners is that there is no means to measure whether the flame in the burner is luminous or not. It is desirable in combustion burners to keep the flame blue. This is so since the carbon material created from a blue flame will be minimal or non-existent. If the flame turns luminous, carbon is created which reduces the efficiency of the burner.
Yet a further disadvantage of previous burners and, in particular, the burner disclosed and illustrated in the above-identified U.S. Reissue patent, is that the flame illustrated just inside the end wall tended to be unstable under certain conditions, particularly where the air flow was high. If a burner flame is not stable, it can lift off the burner grid and, thereby, reduce the efficiency of the burner. Yet a further disadvantage of heaters wherein the flame lifts off the burner grid is that carbon monoxide can be produced which is harmful and possibly dangerous.